Thread grinder workholder



April 13, 1967 E. H. WHITNEY THREAD GRINDER WORKHOLDER 2 Sheets-Sheet 1 Filed Aug. 12, 1964 INVENTOR.

EDGAR H. WH ITN EY ATTORA/EK A ril 18, 1967 E. H. WHITNEY 3,314,197

THREAD GRINDER WORKHOLDER Filed Aug. 12, 1964 2 Sheets-Sheet 2 INVENTOR.

EDG AR H. WHITNEY United States Patent 3,314,197 THREAD GRINDER WORKHOLDER Edgar H. Whitney, Dunnellon, Fla., assignor to Ocala Precision Machining Corp., Dunnellon, Fla. Filed Aug. 12, 1964, Ser. No. 389,120 1 Claim. (ill. 51-232) This invention relates to structural refinements in thread grinding attachments adapted to accommodate themselves to any standard surface grinder, which attachments incorporate registry-maintaining, antifriction, guide devices in connection therewith for aiding the operation thereof.

Without intending to place undue limitations upon the scope of the invention beyond what may be required by the state of the prior art, the particular embodiment may be briefly described as embracing the concept of an improved attachment for surface grinders by means of which such type of machine may be adapted for the precision grinding of threads and allied operations.

It will be helpful to an understanding of my invention first to briefly consider some of the essential points and more important features and aspects thereof, so that same may be kept in mind during subsequent reading of the detailed description of the practical embodiments of my improvements and the illustrations thereof in the hereunto annexed drawings.

Accordingly, it is first to be noted that my invention is embodied in a novel and improved fixture, in the form of an attachment for machines of the surface grinding type, for supporting the work for rotation about an axis predeterminedly disposed with respect to the normal plane of relative traverse between the grinding tool and the work.

The invention is ideally suited for those who may have requirements for ground or special threads in small quantities or the necessity to thread items of hard-to-machine materials, such as tungsten, tungsten-copper, ascalloy, Udimet-SOO, and other high-heat space metals or for mold makers who require threaded cores and faces with or without allowances for shrinkage. The ease with which threads of any contour or pitch may be ground after heat treat make it especially well suited for the average small machine shop.

The invention comprehends a particular construction, arrangement, combination, and relationship of the various elements, components and instrumentalities of a thread grinding fixture as exemplified in the following detailed disclosure wherein the objects hereof, as defined in the below paragraphs, will be apparent.

One general object of the invention is to provide a fixture of the stated character wherein means is provided for varying the degree of movement relative to the axis of rotation of the work with respect to the plane of relative traverse, and in the accomplishment of this general object, I provide a fixture of the defined character having means for maintaining the work fixed in a support for presentation to the grinding tool in desired positions of adjustment relative to the axis.

Another chief object is to provide a fixture of the general character indicated which is of simple construction, is easy to use, and may be employed for precision thread grinding and for other precision grinding work.

Another salient feature hereof is to provide a fixture in- V corporating means for interchanging collar components of a lead screw assembly thereof wherewith to change the threads so as to obtain different pitches.

As one refinement of the invention, I aim to provide position-maintaining means for the movable bearing retainers of the antifriction guiding and aligning components of a fixture in the respect that a spindle or live center is axially receivable for relative longitudinal move- 3,314,197 Patented Apr. 18, 1967 ment in the longitudinal bore of a stationary sleevelike bushing strategically positioned by complemental guide posts or, alternatively, is receivable within a housing. In which form employed, a tubular ball-bearing retainer so circumscribes the spindle as to allow the spindle to float. In either form, the retainer is held so that ball elements carried thereby are disposed in annular receiving spaces provided between the outer wall surface of the spindle and the adjacent inner wall surface of the stationary bushing bore provided by an outer sleeve or housing as the case may be, the ball elements being disposed in simultaneous contact with the spindle and stationary bushing or housing surfaces.

This construction is such as to provide for accurately guided and confined reciprocatory movement on the part of the spindle and to eliminate undesired lateral motion between the parts and to enable the work piece supported by a spindle nose as by a conventional chucking means to be brought into and out of true forming contact with a grinding element. Such alignment of the relatively movable spindle is made possible through the use of the ball element guide devices, and results in prolonging the working life of the spindle, as well as allowing more rapid and more accurate forming operations.

The invention further resides in certain structural and mechanical details, hereinafter set forth, by means of which the aforesaid major objects of the invention are attained and which contribute to the provision of an attachment characterized by extreme flexibility of adjustment and constituting a highly valuable precision adjunct for surface grinders capable of materially enlarging the scope of utility of machine tools of such basic type. One of the subsidiary objects of the invention is, accordingly, the achievement of these satisfactory results by the use of a simple system of the type above indicated.

In addition to the practical advantages which I herein ascribe to my novel fixture, it will be observable that other chief features of the invention reside in the ruggedness and durability of construction which are combined with simplicity of protection against usual but hard conditions of practical use and with simplicity and ease of use and in the fact that while the components are uniquely compact, they are nevertheless readily accessible for maintenance and replacement purposes with a consequent reduction in maintenance costs over related devices heretofore known.

Another object is to provide a fixture of the above mentioned type particularly adapted for the grinding of threads which will give smoothness, ease and precision in handling and operation and will permit of long continuous use with a minimum of need for repair or maintenance on the part of the user, all resulting in important distinct advantages in economy of manufacture, ease of operation, reliability of performance, and capability of ready assembly to provide positiveness and ease of manual control and action under the varying conditions of practical use.

It will be apparent that the physical embodiments delineated, albeit the preferred exemplifications, are only indicative of but two of the multiplicity of ways in and purposes for which the principles of the invention may be employed.

Same are submitted as best known embodiments of the invention in accordance with the patent statutes and are given with a view to illustrating and explaining the precise nature of the principles of the invention and their embodiments for practical use, in order that others skilled in the art to which the invention pertains may be enabled to adapt and modify them in numerous variations and modifications, each as may be best adapted to the conditions of any particular use.

The characteristic features which I consider to be novel with my invention, as to its construction and organization and as to its methods of manufacture and operation, will be better understood from a consideration of the following detailed description forming a part of this specification, when read in conjunction with the illustrations in the accompanying drawings, in which:

FIG. 1 is a side elevational view of the fixture of the invention with certain parts being shown in section;

FIG. 2 is a view taken on the line 2-2 of FIG. 1; and

FIG. 3 is a perspective view of a modified form of the fixture of the invention.

With continued reference now to the drawings, which illustrate typical and preferred embodiments of the invention for the purpose of disclosure and form a part of this specification, I have shown perferred embodiments of the invention in order that the general relation and utility of the components may be better understood.

The invention illustrated in FIGS. 1 and 2 consists of the base or bed plate 16 of the fixture, which base is of generally rectangular form and is adapted to be positioned on and secured to the work supporting table of a surface grinder, as by a conventional magnetic chuck or similar arrangement.

Base may be provided as a completely hardened and ground component and may further be provided with means for setting the base at a desired angle with respect to a reference shoulder on the grinder work supporting table and/or by the use of a cooperant sine bar, for example.

At one end of base 10, a vertically upstanding lead screw retainer or Y-shaped head stock yoke, generally indicated by 12, is provided and is so designed as to be removably secured to the base by means of such as a screw or bolt 16 which may be extended through a bifurcation 18 at the lower extremity 20 of the retainer and threadedly engaged in a suitable opening 22 in the base wherefore the possibility of binding is precluded.

The upper portion of the retainer is provided with a transversely-extending retainer opening therethrough to define an annular seat 24 having outermost outwardly and radially extending annular recesses 26 at its opposite side edges, said opening being adapted to receive a selected one of a plurality of annular collars 30 of a standard U-type lead screw set.

The collar 30, so selected, is securable to the retainer as by a set screw 32 which extends transversely through coaxially aligned openings in the retainer and collar.

Circular end face plates 34 may each be held relative to one of the opposite end faces of the collar as by screws or bolts 36 extendable through suitable openings in opposite faces of the end face plates and retainer in manner to engage the respective end face plate and to hold same in seated position within the respective annular recess 26 and additionally to hold the collar in situ on its seat 24 between said end face plates.

The arms 46, 42 of the retainer will be yieldingly spreadable as to each other by virtue of a verticallyextending slot 44 extending downwardly from the uppermost planar surface 46 thereof and intersecting the retainer opening wherefor the arms, following insertion of collar 30 into said opening, may be drawn into tight embracement relative to each other and upon the collar by means of a bolt 48 extendable through an opening extending transversely through one arm with an inboard extremity thereof being threadedly engageable in an aligned opening in the other arm 42.

As known in the case of a collar of a lead screw set, same is provided with a threaded opening 38 extending transversely therethrough which will be of the screw thread pitch which it will be desired to grind on the work piece.

As aforesaid, in a lead screw set, a plurality of such collars will be provided, each with a different screw thread pitch.

-Rotatably mounted in collar 30 is a spindle or live center 50, which spindle is suitably hardened and ground and is held in position relative to the retainer by means of a lead screw 52 of the lead screw set which may be suitably fixed thereto. The lead screw is threaded so as to be revolvably engageable with the thread of the selected collar.

The lead screw and collars are constituent parts of a lead screw assembly or set and, as is known, can be furnished in any desired lead, even special leads in the case of desirably allowing for any shrinkage factors which may be encountered in any particular type of work.

Secured to the end 56 of spindle 50 is a hand wheel 58 having a suitable handle 60 wherewith complete and positive control is allowed.

The opposite end 62 of the spindle will be provided with means for the interengagement therewith of a conventional spindle nose (not shown) which is suitably threaded and fitted with a standard collet and adapted to be fitted with an adapter plate so as to accept any standard chuck.

It will be understood that the spindle and its supported chuck or collet are adapted to be suitably supported in a floating manner for relative movement as to the base and yoke so as to bring the workpiece into and out of forming engagement with a grinding element.

Means are provided for maintaining the alignment of the spindle during relative movement thereof so that the workpieces carried thereby will be brought into precise registry during work-forming operations, in the form of a guiding subassembly constituted by a pair of guide assemblies, as indicated by 64, each rigidly connected to (as by doweling) and extending upwardly from base 10 so as to be spaced from each other. The guide assemblies have coaxially-aligned transversely-aligned openings 66 extending therethrough and their outboard end faces are covered by anodized retainer plates 68, preferably formed of aluminum, and having apertures 70 therethrough in registry with openings 66.

The retainer plates are secured to their respective guide assemblies as by bolts or screws 72.

Preferentially, but not obligatorily, the retainer plates may be fitted on their inboard faces with suitable felt dust rings or equivalent, all as is conventional.

The guide assemblies will support therebetween, in manner so as to be receivable within the openings 66 thereof, a cylindrical sleeve 76 having a machined and hardened inner surface 78 to allow a uniform diameter throughout the length thereof. Likewise, the spindle will be so formed as to provide through at least a portion 80 of its length a surface which will be machined, hardened or otherwise finished to precise dimensions, after the manner of the interior wall surface 78 of sleeve 76, so that when the spindle moves forwardly or rearwardly, for coaxial longitudinal movement relative thereto, an annular space 82 of uniform dimension is provided between the outer surface of the spindle and the inner surface of the sleeve.

Received in this space is a floating, tubular, ball-bearing retainer 86, the latter having cylindrical, accurately formed, inner and outer surfaces between which radiallyextending, transverse openings are provided, which openings define seats for the reception and retention of antifriction devices, which, as here shown, are in the form of ball bearings 88.

The diameter of each such ball bearing is such that, when held by retainer 86, the same will project beyond the inner and outer cylindrical surfaces of the retainer. Thus, as spindle 50 is motivated, the bearing elements of the retainer will be brought into pressure-confined engagement with the wall surfaces defining the bore of sleeve 76 and the complemental outer surface of the spindle. In this manner, a preloaded ball bushing arrangement is provided.

With the parts of the guide assembly arranged, as shown in FIG. 1, wherein is illustrated the normal positions of the members of the assemblage at the beginning of the outward working stroke of the spindle, it will be observed that retainer 86 is disposed centrally of annular space 82.

With the parts in this position, bearings 88, confined between and in simultaneous contact with the coaxial telescoping poztions of sleeve 76 and spindle 50, are brought under forces of compression.

Upon rotating and forward movement of the spindle, these forces produce positive turning movement of bearings 88 which are engaged simultaneously by both spindle and sleeve, so that retainer 86 is caused to move forwardly concomitantly with the spindle at a controlled, but somewhat reduced or lowered, rate of linear travel.

Due to the pressure loading of bearings 88, and as the forward and rotative progress of the spindle continues, true horizontal movement ensues with an absence of lateral relative motion on the part of the elements of the assembly, all so that the spindle is maintained in proper alignment and registry relative to the grinding element.

In grinding a thread on a (workpiece, base is first positioned at the proper angle with respect to the plane of the grinding wheel, with the grinding wheel being dressed to form the proper thread shape. The grinding wheel is then set so that its center is vertically aligned with the central axis of the workpiece and is fed down onto the work.

Crank 60 is then revolved clockwise to move the work in a manner corresponding to the threads on collar 30 which has been selected for the purpose so as thus to form similar threads on the workpiece.

Where a multiple thread is to be ground, the first thread is formed as by the above described process. The workpiece is then returned to its starting position and a new succeeding collar 30 is substituted for original collar 30, the thread of which succeeding collar will correspond to the angular displacement of the second thread with respect to the first thread at a given axial position on the workpiece. The second thread may then be formed in the same manner as the first thread.

Any desired number of threads may be formed on the workpiece provided the number of collars for the purpose are an integral multiple of the desired number of threads.

-Using the standard U-type lead screw sets, any type and shape of thread can be ground merely by changing the contour of the employed grinding wheel. Square, acme, rolled, buttress and other types and shapes of threads can be attained. Additionally, double or triple threads may be achieved by advancing the cross slide of the grinding /2 or A of the pitch.

Upon the linear travel of the spindle, the outer cylindrical surface of the spindle engages the ball elements of the retainer and forces the same against the complemental inner cylindrical wall of the associated sleeve bore. Since the diameter of each ball element of the bearing retainer is such that it exceeds slightly the width of the annular space which the retainer occupies, each ball element so positioned is placed under compression by its confined engagement with the adjoining spindle and sleeve surfaces. Such loaded or pressure engagement of the ball elements causes the retainer to move linearly with the associated movable spindle but at a relatively reduced or lower rate of travel. That is, the floating bearing-retainer moves at a controlled rate concomitantly with the spindle to provide antifriction holder guidance, all so as to minimize wear and maintain positive alignment between the relatively movable parts. Thus there is allowed a floating characteristic of the ball bearing retainer by the absence of any direct physical connection between the retainer and associated spindle and sleeve.

The present invention, therefore, comprehends providing as an operative sub-assembly an improved positioning means for use in association with an antifriction guide appliance for a thread grinding attachment for a surface grinder, which guide appliance will utilize a floating hearing retainer of the tubular open-ended type and which is interposed, when in use, between a sleeve strategically supported by guide posts and the spindle of the fixture, and to provide in connection therewith novel supporting and positioning means for maintaining the retainer operatively interposed between the guide posts and the spindle in all their working positions, said positioning means serving during active operation thereof to preclude movement on the part of said retainer to positions in which all the antifriction bearing elements positioned therein would be removed from simultaneous pressure engagement with contiguous surfaces of the associated sleeve and spindle.

Thereby, the retainer-positioning means of this character is so formed that it will function to support in definite positions the retainer in its associated sleeve and on the spindle when the latter is fully motivated simultaneously in two direction, i.e. a fore and aft rectilinear movement and a rotary movement, so that the retainer is held automatically in proper positions and adapted to maintain the ball elements thereof under pressure loading in all operative or working positions of the spindle.

With reference now to the modified form of construction shown in FIG. 3, I have shown a base which similarly is adapted to be positioned on and secured to the work supporting table of a surface grinder, such as by a conventional magnetic chuck arrangement.

Base 110 may be provided as a completely hardened and ground component and may further be provided with means for setting the base at a desired angle with respect to a reference shoulder on the grinder work supporting table and/or by the use of a cooperant sine bar, for example.

At one end of base 110, a vertically upstanding lead screw retainer 112 is provided for removable securement to the base such as by a screw or bolt 116 extendable through a bifurcation 118 at the lower extremity of the retainer and threadedly engaged in a suitable opening in the base.

The upper portion of the retainer is provided with a transversely-extending retainer opening therethrough to define an annular seat, said opening being adapted to receive a selected one of a plurality of annular collars of a standard V-type lead screw set.

The arms 140, 142 of the retainer will be yieldingly spreadable as to each other by virtue of a verticallyextending slot 144 extending downwardly from the uppermost planar surface thereof and intersecting the retainer opening wherefor the arms, following insertion of the collar into said retainer opening may be drawn into tight embracement relative to each other and upon the collar by means of a bolt 148 extendable through an opening extending transversely through one arm with an inboard extremity thereof being threadedly engageable in an aligned opening in the other arm 142.

The collar so selected is securable to the retainer as by a set screw which extends transversely through coaxially aligned openings in the retainer and collar.

In this modification, the end face plates have been dispensed with.

A spindle 150 is extendable through the collar opening and is in threaded engagement therewith by means of a lead screw 152 of the lead screw assembly which interengages the internal thread of the collar.

Secured to one end of spindle 150 is a hand wheel 158 having a suitable handle 160.

The opposite end of the spindle will be provided with means for the interengagement therewith of a conventional spindle nose 163 which is threaded and fitted with a standard collet 165 and is adapted to be fitted with an adapter plate so as to accept any standard chuck.

Means are provided for maintaining the alignment of the spindle during relative movement thereof so that the work pieces carried thereby will be brought into precise registry during work-forming operations, in the form of a guiding housing 167 which is suitably provided with securing means for allowing the stationary securement of the housing relative to the base.

The end faces of the housing are covered by suitably apertured retainer plates 168, secured to the housing as by bolting 172 and fitted on their inboard faces with suitable felt dust rings or equivalent, all as is conventional.

The housing is provided with a precision bore transversely therethrough from end to end, which bore is alignable with the apertures in the retainer plates so as to define a cylindrical wall therewithin having a machined and hardened inner surface to allow a uniform diameter throughout the length thereof. Likewise, the spindle will be so formed as to provide along at least that portion of its length which is extendable through the housing a surface which is machined or otherwise finished and hardened to precise dimensions, in the same manner of the interior wall surface of the housing bore, so that when the spindle moves forwardly or rearwardly, for coaxial longitudinal movement relative thereto, an annular space of uniform dimension is provided between the outer surface of the spindle and the adjacent wall surface of the bore, in which annular space the floating, tubular, ballbearing retainer, is receivable.

As in the form shown in FIGS. 1 and 2, openings through the bearing retainer define seats for the reception and retention of antifriction devices in the form of ballbearings.

As spindle 150 is motivated, the bearing elements of the retainer are brought into pressure-confined engagement with the wall surfaces defining the housing bore and the complemental outer surface of the spindle, to provide a preloaded ball bushing arrangement.

With the parts in situ, the ballbearings confined between and in simultaneous contact with the housing bore and spindle, are brought under forces of compression. Upon rotating and forward movement of the spindle, these forces produce positive turning movement of bearings, so that the retainer is caused to move forwardly concomitantly with the spindle at a controlled, but somewhat reduced or lowered, rate of linear travel. Due to the pressure loading of the ballbearings, and as the forward and rotative progress of the spindle continues, true horizontal movement ensues with an absence of lateral relative motion on the part of the elements of the assembly, all so that the spindle is maintained in proper alignment and registry relative to the grinding element.

This form of the invention, therefore, comprehends providing as an operative sub-assembly an improved positioning means within a housing for use in association with an antifriction guide appliance for a thread grinding attachment for a surface grinder, which guide appliance will utilize a floating bearing retainer of the tubular openended type and which is strategically interposed, when in use, between the wall of the housing bore and the spindle, and to provide in connection therewith novel supporting and positioning means for maintaining the retainer operatively interposed between the housing and the spindle in all their working positions, said positioning means serving during active operation thereof to preclude movement on the part of said retainer to positions in which all the antifriction bearing elements positioned therein would be removed from simultaneous pressure engagement with contiguous surfaces of the associated housing and spindle as the spindle is motivated in two directions, i.e. a fore and aft rectilinear movement and a rotary movement, so that the retainer is held automatically in proper positions and adapted to maintain the ball elements thereof under pressure loading in all operative or working positions of the spindle.

The claims are desired to include within the scope thereof all of said suitable variations, modifications and equivalents by which substantially the results of the invention may be obtained through the use of substantially the same or equivalent devices or means. Accordingly, limitation hereof should only be made as determined by a proper interpretation of the prior art and the scope of the subjoined claims, in which it is my intention to claim all novelty inherent herein as broadly as possible.

I therefore particularly point out and distinctly claim as my invention:

A portable work-holding fixture for mounting on the table of a grinding machine comprising,

a fiat elongated base,

an elongated head stock yoke supported upwardly of the top surface of said base and having a split upper portion and resilient arms providing a collar retainer opening therethrough,

an internally threaded collar in said retainer opening,

locking means threaded in the split upper portion of said arms for drawing said arms into tight embracement upon said collar thereby precluding rotation of said collar within said retainer opening,

a live center member rotatably mounted in said head stock yoke,

a lead screw on said live center member adjacent one end thereof and revolvably engageable with the thread of said collar,

said threaded collar being releasably fixed in said retainer opening and said lead screw being releasably fixed to said live center member,

said collar and lead screw constituting a set of the screw thread pitch desired to be ground on the work piece,

means fixed to said live center for the rotating of same,

gripping means at the opposite end of said live center for holding a work piece,

and aligning means for maintaining the alignment of said live center during relative movement thereof including a guiding subassembly supported upwardly of the top surface of said base and a longitudinallyextending bore through said guiding subassembly for rotatably supporting said live center and a cylindrical sleeve receivable within the bore and an anti-friction means disposed within the bore and sleeving said live center and a plurality of bearing elements carried by said anti-friction means and bearing pressureconfining engagement with said bore and said live center as said anti-friction means is supported in definite positions within said sleeve and on said live center when the latter is fully motivated in rotary and rectilinear movements.

References Cited by the Examiner UNITED STATES PATENTS 1,411,191 3/ 1922 Schellenbach 5195 1,594,407 8/1926 Durkee 5l95 2,311,815 2/1943 Briney 5195 2,347,766 5/1944 Briney 5l95 2,362,288 11/1944 Melin 5 l2 19 X 2,420,296 5/ 1947 Bishop 5195 HAROLD D. WHITEHEAD, Primary Examiner. 

